1. Field of the Invention
This invention relates to loading dock equipment and in particular to dock levelers that are used to span the distance between a loading dock and the bed of a vehicle. Specifically, it deals with a specific type of lip for a dock leveler.
2. Prior Art
A conventional loading dock for transport vehicles typically has a dock leveler with a dock bumper placed on each side of the dock opening mounted on the dock face in a fixed position. The width of the dock leveler is usually limited to a maximum width of seven feet because if the bumpers are placed wider apart there is a risk that the vehicle, which is limited in width, may miss the bumper and strike the dock leveler. Consequently, the probability of damage is relatively high if the vehicle strikes the end of the leveler. Some specialty dock levelers are wider than seven feet to provide space for wider than normal cargo. Examples of these devices are shown in U.S. Pat. Nos. 5,881,414 and 6,070,203. U.S. Pat. No. 4,420,849 illustrates a dock leveler with bumpers that fold away to accommodate wide loads, but with all of these devices the width of lip is still limited by the space between the dock bumpers. U.S. Pat. No. 6,081,954 describes a dock leveler with a lip that extends linearly rather than rotating in the conventional manner. However the distance between the bumpers would still limit the width of the leveler.
Segmented lips are generally known. These are manually operated by the dock worker.
There is a need for a dock leveler which has a lip that is wider than the distance between the dock bumpers. One method of shipping cargo employs two rows of wheeled carts on a transport vehicle. When a row of carts is pulled from the transport vehicle onto the loading dock, the outer wheels of the carts will extend beyond the seven foot width of a conventional dock leveler lip. Thus the wheels of the cart may fall into the gap between the back of the transport vehicle and the front of the dock bumper, and the movement of the carts may be impeded.
A potential problem with increasing the width of the lip is interference with the side of the transport vehicle if the vehicle is not properly centered on the loading dock. This problem is not unique to wide lips. Such interference is possible even on standard width lips if the door opening of the vehicle is not much greater than the width of the lip. Dock levelers having a lip with a selectable segment at one or both sides have been constructed but with manual activation requiring the operator to reach behind the lip to engage a latch. Such lips did not allow the width of the lip to exceed the distance between the bumpers.
Given the problems in the prior art, it is an object of this invention to define a dock leveler that has the versatility to employ a lip of different widths.
It is another object of this invention to provide for a dock leveler that allows a wide lip to be safely used.
It is yet another object of this invention to provide a dock system employing a segmented lip that allows the operator to select and operate the lip segments automatically from the dock floor.
This invention is a dock leveler having a lip with selectable segments at either side. The segments may remain pendent or be selected to be extended with the lip. The lip may be of conventional configuration placed between the dock bumpers or may be wider than the space between the bumpers. Thus the lip may be almost as wide as the opening in the back of the transport vehicle and all the wheels of the cart may roll easily from the bed of the transport vehicle over the lip and onto the dock leveler. If the transport vehicle is not properly centered on the loading dock then the operator may select more lip segments on one side than the other.
The first preferred embodiment of this invention employs a dock leveler that is mounted in a recessed pit of conventional construction. The dock leveler may be as wide as necessary to provide access to the transport vehicle. A lip is mounted to the front of the deck of the leveler and pivoted in a conventional manner. At each side of the lip are narrower lip segments. The bumpers are supported with vertical plates so that the plates may fit in the gap between the lip and the lip segments. Thus the lip segments may be stored behind the bumpers and the effective width of the lip may be greater than the space between the bumpers. The lip segment itself may be of conventional configuration where the back edge of the lip abuts the front of the deck when extended, or it may be of the xe2x80x9cbarrier lipxe2x80x9d configuration where the rear of the lip is extended above the top of the deck to provide a run-off guard when the lip is pendent. While either lip configuration may be used with this invention, the lip segments are preferably of conventional configuration so that the segments that are left pendent do not obstruct movement of wide cargo over the dock leveler. Each lip segment has a hydraulic cylinder and a control valve. The operator may observe the relationship of the transport vehicle and the dock leveler and then move switches on the control panel to select the segments that are to be extended with the lip.
The second preferred embodiment is similar to the first except that the lip segments are selected manually and extended mechanically as the lip extends. They are retracted mechanically as the lip retracts.
The third preferred embodiment is similar to the second except that the lip segments are selected manually and extended by springs that urge them to the extended position. They are retracted as the lip retracts.
The fourth preferred embodiment is similar to the first except that the dock leveler has a lip that retracts linearly rather than by rotation. The segments may be extended and retracted hydraulically or mechanically as in the previous embodiments.